1. Technical Field
The present invention relates to an electroacoustic transducer in which a diaphragm supported by a carrier portion and an electrode portion opposed to the diaphragm at a predetermined interval are accommodated in a housing, such as a microphone for use in a hearing aid or the like.
2. Background Art
As a conventional microphone for use in a hearing aid, as disclosed in U.S. Pat. No. 6,169,810 B1, there has been known an electroacoustic transducer in which a diaphragm having a conductive layer and an electrode portion having an electret layer are accommodated in a housing in a state where the electrode portion is opposed to the diaphragm at a predetermined interval by clamping the diaphragm on a frame-shaped carrier having inwardly-extending supporting portions and placing the electrode portion on the supporting portions with spacers interposed therebetween.
However, as for such a diaphragm clamped on a frame-shaped carrier having inwardly-extending supporting portions, the amplitude in response to sound waves is greatly limited compared to a case of no supporting portions because the supporting portions are a point where the vibration of the diaphragm is initiated.
In addition, since the carrier is a rectangular shaped frame body, there is a problem that the carrier cannot keep its flatness due to a strain or twist which is applied thereto along the diagonal. Such a problem has an undesirable influence on the tension of the diaphragm or the interval between the diaphragm and the electrode portion. Therefore, since it is necessary to prevent the carrier from being subject to a strain or twist at the time of assembling an electroacoustic transducer, the stable manufacture of an electroacoustic transducer is difficult.
In order to solve the above-mentioned problems, the object of the present invention is to provide an electroacoustic transducer, characterized in that the desirable tension of a diaphragm is not changed over time, the interval between the diaphragm and the electrode portion can accurately be kept or maintained over time, the amplitude of the diaphragm in response to sound waves can be increased, and the influence of an external force can be reduced.
According to an aspect of the present invention, there is provided an electroacoustic transducer comprising a carrier portion, a diaphragm supported by the carrier portion, an electrode portion opposed to the diaphragm at a predetermined interval, and a housing for accommodating the diaphragm and the electrode portion, wherein the carrier portion has a saucer-like shape, at the bottom surface of which a plurality of posts are provided, and wherein the surface of the periphery of the carrier portion and the end surfaces of the posts are in the same plane, the diaphragm is bonded to the surface of the periphery of the carrier portion and the end surfaces of the posts, and the electrode portion is fixed to the end surfaces of the posts which are covered by the diaphragm with spacers interposed therebetween.
According to another aspect of the present invention, in the above-mentioned electroacoustic transducer, the diaphragm is formed in a film shape having a conductive layer provided on the surface of the diaphragm which faces the electrode portion or the other/opposite surface of the diaphragm, and the electrode portion has an electret layer and also has protruding portions provided on the surface of the electrode portion which faces the diaphragm, the protruding portions functioning as the above-mentioned spacers.
According to another aspect of the present invention, in the above-mentioned electroacoustic transducer, a sound guide port is provided at the bottom of the carrier portion, and the inside of the housing is divided into a first acoustic chamber and a second acoustic chamber by bonding the bottom of the carrier to the bottom surface of the housing and bonding the periphery of the sound guide port to the inside wall of the housing.
According to another aspect of the present invention, in the above-mentioned electroacoustic transducer, the carrier portion is formed by an etching process.